Switching types of brake fluid (5.1 to 4)

[priorityR6]

Hi - noob here!

Just bought an 09 R6 to replace my old and tired 636. Love it so far.

Quick question though:

The guy I bought it from had put DOT 5.1 fluid in the brakes. The brakes are spongy and I'd like to bleed them. I've always used DOT 4 in my bikes. My understanding is that you are not supposed to mix 5.1 and 4.

Can I just run a bunch of DOT 4 through in order to replace all of the 5.1 that's in the system? I think I read something about using DOT 4 after 5.1 having an effect on the seals (around the brake pistons)?

Thanks,

Brian

[Rocky5000100]

Yes, just run a bunch through to clear out the old stuff.

[priorityR6]

Not to sound more noobish but should I bother to go back to 4 from 5.1 in the first place? Bike is mostly for the track. I never used to wrench on my own stuff. Just looking to learn.

[Rocky5000100]

Originally Posted by priorityR6

Not to sound more noobish but should I bother to go back to 4 from 5.1 in the first place? Bike is mostly for the track. I never used to wrench on my own stuff. Just looking to learn.

Yes. Get 4.

Motul RBF600 or ATE Superblue are the two best choices.

[SlickXR6]

Alot of people prefer the DOT4. Just be aware. DOT 3,4, and 5.1 ( NOT DOT 5) are glycol based. Where DOT 5 is silicon based. DO NOT put DOT 5 in your system. IMO mixing (even though possible) is a bad idea, do a good flush if you want to use DOT4. Some DOT 4 fluids have higher boiling points than DOT 5.1, so there are reasons why they do it. When it comes down to it, they put 5.1 in the factory for a reason, unless youre competative enough to actually feel the difference, just leave it alone

Just my 2 cents.